Aux Drive Belt R129

[John042]

Hi. I,m considering changing the aux drive belt on my 1998 320sl V6. Not for any problems other than its shiney appearance and the fact of no history if it's every been changed (106k) Is it a sevice item? Also, is it advisable to also replace the tensioner and ldler pulley at the same time? I read somewhere that the early tensioners could give problems? Thanks for any advice. John C

[74merc]

I haven't heard of many pulley failures on the M112 engine but I would be concerned about the health of the harmonic balancer (the pulley on the crankshaft with the rubber innards). Normally the rubber on these starts to delaminate, then finds it's way round the engine bay at speed.

[John042]

Thanks 74merc. I hadn't considered the crank pulley until you mention it. There are quite a few posts, mostly originally US on the subject concerning recalls but not in UK? I guess it's on condition? An interesrting item to remove on an auto!! However were all V6's fitted with a hamonic type crank pulleys? Thanks for your interest and replies. John C.

[chris333]

The crankshaft pulley failed on my '98 SL500. Fortunately I got it replaced before it could do any damage, but apparently if you drive it for too long in that condition, it can machine a hole in the front of the block..not a good day.

Best to change it!

[John042]

Thanks Chris333. Point taken. What's the best way of locking the crankshaft on an auto when removing /refitting the bottom pulley bolt please? Cheers John C

[chris333]

Sorry, I can't help with that one. I had mine done at my local MB Specialist.

[74merc]

On some of the M112 engined cars there is a cutout to lock the flywheel, but mine and probably yours won't have this. I had a 98 C280. AFAIK, the gearbox and engine have to be split to get access to lock the flywheel and a breaker bar used to undo the bolt on the pulley.